Network slicing serving function

ABSTRACT

Techniques for implementing a network slice selection function are described. In one example aspect, a network slice instance request message is received for a user device. In response, the network slice selection function transmits a response message that includes information about allowed network slice instances for the user device. The allowed network slice instances include network slice instances that are available in the registration area of the user device.

CROSS REFERENCE TO RELATED APPLICATIONS

This patent document is a continuation of and claims priority toInternational Patent Application No. PCT/US2018/023435, filed on Mar.20, 2018, which claims the benefit of priority of U.S. ProvisionalPatent Application No. 62/473,760, filed on Mar. 20, 2017. The entirecontent of the before-mentioned patent application is incorporated byreference as part of the disclosure of this document.

TECHNICAL FIELD

This document relates to systems, devices and techniques for wirelesscommunications, including next generation network architecture.

BACKGROUND

Efforts are currently underway to define next generation communicationnetworks that provide greater deployment flexibility, support for amultitude of devices and services and different technologies forefficient bandwidth utilization.

SUMMARY

This document describes technologies, among other things, for providinga serving function for network slice resources to user devices in awireless communication network.

In one example aspect, a network function, called network slicingserving function (NSSF) for a public land mobile network (PLMN) isdisclosed. The network function has the knowledge of the network-wideaccess and mobility management (AMF), the NSSF implements slice-levelservice mapping for a given slice-specific Network Slice SelectionAssistant Info (S-NSSAI) and selects a target network slice instance(NSI) based on one or more operational parameters. The NSSF identifiesslice level policy for network slices. The NSSF collects slice-levelstatistics from AMF of its serving PLMN and supports NSSF's operation.

In another example aspect, a wireless communication system is disclosedin which the NSSF is implemented as a separate entity in the network.The NSSF may communicate with other network entities via an interfacecalled Nnssf.

In yet another example aspect, a network function repository function(NRF) that includes the NSSF is disclosed. The NRF provides the NSSFfunction and further provides an isolation between network slices.

In yet another example aspect, a procedure for registering a userequipment (UE) in a mobile network is disclosed. The procedure includesreceiving a network topology, and based on the network topology,determining a set of network slice instances available in the UE'sregistration area, and deciding whether to assign serving the UE to anew serving AMF, and causing a current serving AMF to cache informationfrom the NSSF for future use.

In yet another example aspect, a network function that assigns amobility function for serving network slice instances to a user deviceis discloses. The network function stores a mapping between a pool ofthe mobility functions and a set of core network slice instances beingserved by the pool, and selectively updating the mapping based on UEmobility or a change in an operator policy or a topology of the mobilenetwork.

In yet another example aspect, a method for establishing a packet dataunit (PDU) session for a UE is disclosed. During the establishing of thepacket data session, a mobility function uses locally cached informationabout a UE's context and determines its ability to serve the UE. If themobility function is not able to serve the UE, the task of serving theUE is handed over to a second mobility function.

In yet another example aspect, a network architecture that supportsnetwork slicing roaming in a mobile network that uses home routing isdisclosed.

In yet another example aspect, a PLMN architecture is disclosed. ThePLMN includes an entry point NRF that is a designated entry point forcommunication with another PLMN's entry point NRF and exchanges messagesto manage a single connection point for carrying NRF look-ups betweenthe PLMNs.

In some embodiments, the NSSF function may be implemented by anapparatus that includes a memory, a processor and at least one networkinterface, wherein the processor reads instructions from the memory andimplements the NSSF function.

In some embodiments, the disclosed NSSF may be embodied as processorexecutable code and stored on a computer-readable program medium.

In one example implementation, a method for facilitating operation of awireless device in a wireless communication network includes receiving,at a network slice selection function in a communication network, anetwork slice instance request message indicative of a configurednetwork slice selection assistance information for a user device ispresently configured, a subscribed network slice selection assistanceinformation for which the user device has subscribed, and an identity ofa registration area that the user device is associated with, andtransmitting, in response to the network slice request message, aresponse message that includes information about allowed network sliceinstances for the user device. A network slice corresponds to a virtuallogical network that is optimized for at least one network service. Theallowed network slice instances comprise network slice instances fromthe registration area that are available for the user device.

In another example implementation, a method for facilitatingestablishment of a packet data session for a user device includesreceiving a verification request from a mobility function in a corenetwork of a communication network, the verification request identifyingthe user device, a current registration area of the user device and anetwork slice assistance information requested by the user device forestablishing the packet data session, and transmitting a response to themobility function identifying a network slice instance available for thenetwork slice assistance information requested by the user device.

In another example implementation, a method of wireless communicationincludes receiving by a network device in a wireless network a requestfor a data session from a user device, the data session requestidentifying an identification for the user device and a target datanetwork for the data session.

In yet another example implementation, a method of communication,performed in a communication network a first and a second PLMNs includesoperating an entry point function in the first PLMN at a logical levelabove a first plurality of slice level repository functions in the firstPLMN to receive resource look-up requests from a second plurality ofslice level repository functions in the second PLMN, and communicatingwith the first plurality of slice level repository functions in thefirst PLMN to generate a response for the resource look-up requests.

In yet another example implementation, a method implemented by a userdevice includes registering for operation in the wireless network usingnetwork slice assistance information for which the mobile device isconfigured, and indicating a target set of network services that themobile device wants, receiving a set of allowed network slice assistanceinformation and a session identification, and performing furthercommunication in the wireless network using the set of allowed networkslice assistance information and the session identification.

In yet another example implementation, a method for providing networkservices to a mobile device operating in a visited network includesreceiving, by a mobility function in the visited network, from themobile device, a message identifying requested network slice assistanceinformation and an identification of the mobile device, obtainingidentification of a session management function in a home network forthe mobile device, wherein the obtaining is performed querying a networkrepository function in the home network for the mobile device with therequested network slice assistance information, and acting as apeer-to-peer interface for relaying the another set of resource look-uprequests to a single entry point function in the second PLMN.

In yet another example implementation, a method, implemented by a userdevice includes registering for operation in the wireless network usingnetwork slice assistance information for which the mobile device isconfigured, and indicating a target set of network services that themobile device wants, receiving a set of allowed network slice assistanceinformation and a session identification, and performing furthercommunication in the wireless network using the set of allowed networkslice assistance information and the session identification.

In yet another example implementation, a method for providing networkservices to a mobile device operating in a visited network includesreceiving, by a mobility function in the visited network, from themobile device, a message identifying requested network slice assistanceinformation and an identification of the mobile device, selecting asession management function serving the visited network, and providingidentification of a network repository function in a home network forthe mobile device and the requested network slice assistance informationto the session management function serving the visited network for thesession management function serving the visited network to look up asession management function in the home network for the mobile device.

The details of one or more implementations are set forth in theaccompanying attachments, the drawings, and the description below. Otherfeatures will be apparent from the description and drawings, and fromthe claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example non-roaming 5G system architecture using aService-based representation.

FIG. 2 shows an example non-roaming 5G system architecture using aReference point-based representation.

FIG. 3 show an example implementation of Network Slicing for networkoptimization for specialized network services.

FIG. 4 shows an example of a non-roaming 5G system architecture withnetwork slicing support—Service-based Representation.

FIG. 5 shows an example of a non-roaming 5G system architecture withnetwork slicing support—Reference point-based Representation.

FIG. 6 shows an example of messages exchanged for NSSF operation duringUE access registration.

FIG. 7 shows an example of messaged exchange for NSSF operation duringUE data session establishment.

FIG. 8 shows an example implementation for NSSF home-routed roamingsupport during UE registration.

FIG. 9 shows an example architecture of vAMF looks up from the hNRF forhSMF.

FIG. 10 shows an example architecture of vSMF looks up from the hNRF forhSMF.

FIG. 11 shows an example of a hierarchy network repository function(NRF) look-up.

FIG. 12 is a block diagram of an example communication apparatus.

FIG. 13 is a flowchart for an example method of facilitatingregistration of a mobile device in a communication network.

FIG. 14 is a flowchart for an example method for facilitatingestablishment of a packet data session for a user device.

FIG. 15 is a flowchart for an example method of wireless communicationsession performed during packet data session establishment for a userdevice.

FIG. 16 is a flowchart for an example method of operating an entry pointfunction in a communication network.

FIG. 17 is a flowchart for an example method of wireless communicationimplemented by a mobile device.

FIG. 18 is a flowchart for an example method for providing networkservices to a mobile device operating in a visited network.

FIG. 19 is a flowchart for another example method for providing networkservices to a mobile device operating in a visited network.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

The evolution to the 5G is work in progress. One 5G system networksolution is to evolve the 5G system to support Network Slicing. Thearchitectural purpose of network slicing is to leverage the networkfunction virtualization network management technique to enable moreefficient logical network implementation to support variety of emergingnext generation network services. It is expected that the nextgeneration 5G network services will impose vast diverse and conflictingsystem requirements towards 5G system such that, it is impossible foroperators to deploy one-size-fits-all network solutions. Therefore,network slicing the operator's network deployment enables more costeffective and optimized network solutions to support variety of nextgeneration 5G network services.

The present document discloses, among other things, a network-sidefunction, called the network slice serving function (NSSF), that can beimplemented to support the use of network slice instances in futuremobile networks. As further described herein, the NSSF may beimplemented as a separate functional entity (e.g., dedicated hardwareplatform(s)), or may be included with another existing network functionsuch as the network repository function (NRF).

FIG. 1 shows an example non-roaming 5G system architecture usingService-based representation.

FIG. 2 shows an example non-roaming 5G system architecture usingReference point-based representation.

The rectangle boxes in FIG. 1 and FIG. 2 represent the network functions(NFs) that were defined for 5G system as documented in TS 23.501. Thekey set of network functions are:

-   -   Authentication Server Function (AUSF)    -   Core Access and Mobility Management Function (AMF)    -   Data network (DN), e.g. operator services, Internet access or        3rd party services    -   Structured Data Storage network function (SDSF)    -   Unstructured Data Storage network function (UDSF)    -   Network Exposure Function (NEF)    -   NF Repository Function (NRF)    -   Policy Control function (PCF)    -   Session Management Function (SMF)    -   Unified Data Management (UDM)    -   User plane Function (UPF)    -   Application Function (AF)    -   User Equipment (UE)—may include a mobile device or a user device    -   (Radio) Access Network ((R)AN)    -   Network Slice Selection Function (NSSF), as disclosed in the        present document.

More details on the definitions of each network functions shall refer toTS 23.501, which is incorporated by reference in its entirety.

FIG. 3 show an example implementation 300 of Network Slicing for networkoptimization for specialized network services. As depicted in FIG. 3,today's 4G networks that offer communication service via phones (e.g.,voice, text, internet), will evolve into a 5G network in which allmobile services via all types of devices may be offered. For example,mobile phones and tablets may operate at large bitrates such as 20 Gbps,while in some areas, networks may operate with a large density ofwireless devices, such as Internet of Things (IoT) configurations with200,000 or more devices per square kilometer. At the same time, quickresponse and mission critical applications such as autonomous driving,which require responses times of the order of 1 msec or less, may alsobe supported by the 5G network infrastructure. To enable such a widerange of configurations and services, and offering connectivity tovarious industries such as communications/internet, logistics,agricultural, climate, automobiles and factory settings, an architecturethat uses network slices has been proposed. Using network slices, theright level of network resource may be allocated to a particular mobiledevice, in order to meet the desired service requirements. Such networkslices may include, for example, large bandwidth slices, high densityslices, mission critical slices, and so on.

FIG. 4 shows an example of a non-roaming 5G system architecture withnetwork slicing support using a service-based Representation. Thevarious architectural blocks are similar to as described in FIG. 1 andFIG. 2. Notably, an additional functional block, called the NSSF, isincluded in FIG. 4. Various embodiments and aspects of this networkfunction are described in the present document.

FIG. 5 shows an example of a non-roaming 5G system architecture withnetwork slicing support using a reference point-based Representation.The above-mentioned NSSF is described in the core part of the controlplane, which is a core part of a network slice.

In some embodiments, a network function, called network slicing servingfunction (NSSF) for a public land mobile network (PLMN) may beimplemented. The network function has system-wide knowledge of thetopology mapping of Core Network Part network slice instance (NSI) toaccess and mobility management (AMF) for a given PLMN, the NSSFimplements service mapping for a given slice-specific Network SliceSelection Assistant Info (S-NSSAI) and selects a target instance of anetwork slice based on one or more operational parameters. The NSSFidentifies slice level policy for network slices. The NSSF collectsslice-level statistics from AMF of its serving PLMN and supports NSSF'soperation.

This document describes a next generation 5G mobile system architecturethat includes a new network function referred as Network Slicing ServingFunction (NSSF) to support the network slice instance (NSI) selection inboth RAN sharing and non-sharing virtual environment. The NSSF is a partof the 5G core network function and it interfaces with the operator'smanagement system that controls and manages the NSIs according to theoperator defined network slice profile that specifies the requiredend-to-end system resources, infrastructure, performance and servicerequirements to support specific target set of services.

3GPP has been working on the next generation 5G system architecture andthey are captured in the two forms as shown in FIG. 1 and FIG.2—traditional reference point based and new service basedrepresentations. However, the details on the network slicingarchitecture on the 5G system have not been fully addressed. Whennetwork slicing is supported over the 5G system, it will be organizedinto network slices operating as the virtual logical network which isoptimized to support one or more set of network services. As describedbefore, FIG. 3 presents the concept of network slicing.

The notions of the two architecture representations are as follows:

-   -   A service-based representation, where network functions (e.g.        AMF) within the control plane enables other authorized network        functions to access their services. This representation also        includes point-to-point reference points where necessary.    -   A reference point representation, focusing on the interactions        between pairs of network functions described by point-to-point        reference point (e.g. N11) between any two network functions        (e.g. AMF and SMF) is depicted when some interaction exists        between these two network functions.

Prior to network slicing can be deployed over the 5G system, 5G operatorneeds to develop the network slice template by leveraging the NetworkFunction Virtualization (NFV) management technique to manage the targetservice. A network slice template defines the setup of the slice,including the system components that need to be instantiated, thefeatures to enable, configurations to apply, resource assignments andall associated workflows, including all aspects of the life cycle (suchas upgrades and changes). The template contains machine-readable partswhich support automation. Leveraging cloud technologies means thatmultiple slices with different service properties are still able to runover a common set of resources. Furthermore, all virtualized networkfunctions execute over a common pool of hardware and commoninfrastructure/platform software.

When operator deploys the target network service(s), identified by oneor more S-NSSAI(s), in instance of network slice (NSI) is instantiatedaccording to the network slice template. The virtualized part of thenetwork slice instance which is comprised of a cooperating set ofVirtual Network Functions (VNFs) would be instantiated via NFVorchestration platform according to the slice template, while thenon-virtualized part would be created and configured by thenon-virtualized management environment.

Once the NSI becomes available, it can then operate as a logical networkto serve its subscribers. In 3GPP 5G system, it is expecting a givensubscriber's device (i.e. UE) could be associated with more than one NSIto access multiple network services simultaneously.

This document discloses a new network function referred as NetworkSlicing Serving Function (NSSF) to support UE attachment to the networkslice instance (NSI) over a 5G virtualized system which may or may notbe RAN sharing. The NSSF is part of the 5G core network function and itinterfaces with the operator's NFV service orchestration managementsystem that controls and manages the life cycle of the NSI according tothe network slice template on the specified end-to-end system resources,infrastructure, performance and service requirements.

Further details on the design of NSSF are described in the followingsections. Section headings are used only to improve readability, and donot limit the scope of described technology only to the correspondingsections.

I. Brief Summary

In the sections below, a functional overview of the network sliceselection function is provided. The various aspects are highlighted byusing two examples for both roaming and non-roaming mobile devices in acommunication network. One example relates to the initial registrationof a mobile device (UE) in a registration area. The other examplerelates to the various steps performed when a mobile device requests adata session.

II. NSSF Functional Overview

NSSF implementations may include one or more of the followingfunctionalities.

It is a network function which has the overall knowledge of thesystem-wide mapping of the AMF to Core Part NSI topology for a givenPLMN.

For example, the NSSF may recognize the availability of the set ofactive NSI(s) corresponding to the registration areas and for whichentry point (i.e. AMF) that is accessible to the specific set of NSI(s)and the corresponding serving NRF(s)

It may be noted that having AMF/AMF pool to serve every single NSIacross the system's registration areas is NOT a scalable deployment inorder to maintain consistent AMF to Core Part NSI mapping topology andconfigurations across all AMF/AMF pool. As a result, AMF/AMF pool shouldbe organized to support the specific set of NSI(s) that are catered forparticular network service deployment.

The NSSF may also support slice-level service mapping for a givenS-NSSAI to select the target NSI by taking into account of the servingMNO, Service or OTT providers, UE's location, time window etc.

It identifies the slice-level policy for the slices which are specifiedby the PLMN. For example, a network slice for the mission-criticalservice must get higher priority than the other eMBB slice; or rejectingUE eMBB slice service if there is an existing UE associated “active” NSIfor mission critical which has higher priority.

It collects slice-level related statistic from AMF for its serving PLMN(e.g. collecting the number of UEs being assigned to a particular NSI)to support slice management operation (e.g. scale in/out)

III. Example of 5G System Architecture with NSSF Support

There are two options for the system architecture to support NSSF.

III.A. Option-1: Introducing a Separate New Logical Network Function

In this option, a new logical network function entity, i.e. NSSF, isadded to the 5G system. Roaming and non-roaming 5G system architecturein both the service-based and the reference point-based representationscan be described as follows:

For the service-based architecture, new service based interface Nnssf isintroduced to support the NSSF functionality that were described above.

For the reference point based architecture, new reference points N99 isintroduced to support the NSSF functionality that were described above.

III.B. Option-2: Integrate NSSF into NRF that is Operating Above theSlice Level

In this option, generally, there is no change of existing architecture.However, a new function, called a hierarchical NRF, of which the toplevel of NRF serves at the system level supporting not only thediscovery and selection of the network function that is operated abovethe slice level, but also supporting the NSSF's functionality asdescribed earlier, is added to the existing architecture.

The second level of the NRF is operating at the slice level whichsupports the discovery and selection of the network function within theslice. With this approach, it can support network function isolationbetween network slices which is important requirement for networkslicing support—i.e. slice isolation.

IV. NSSF Operation Overview

The following describes the overview of the operations of the NSSFduring the UE registration and data session establishment.

One building block is the Network Slice Selection Assistant Info(NSSAI). NSSAI is a collection of Slice specific NSSAIs (S-NSSAIs).S-NSSAI may include two pieces of information:

Slice type or referred as Slice Service Type (SST) which is used toidentify a specific type of network slice, and

Slice Differentiator (SD) which is used to identify a specific slice fora given slice/service type.

In addition, the set of network functions are referred to support thefunctional descriptions of how NSSF operates to support UE registrationand PDU session establishment during non-roaming and roaming scenarios.

IV.A. NSSF Operation During UE Access Registration

FIG. 6 describes the NSSF operation during the UE registration whenaccessing to the 5G mobile network.

1. UE registers with the 5G system with the configured NSSAI which wasconfigured by the UE's home PLMN and is used to indicate the target setof network services that the UE would be interested in.

2. & 3. 5G Access Network (e.g. 5G RAN) interprets the NSSAI infoprovided by the UE in order to route the UE's registration request tothe target AMF or a pool of AMFs (i.e. AMF pool) together with theconfigured NSSAI info. If 5G Access Network does not recognize theNSSAI, the UE's registration request will be routed to the defaultserving AMF or AMF pool.

4. The selected serving AMF consults with the UDM on the UE'ssubscription to verify what are the set of S-NSSAI(s) that the UE hassubscribed for.

5. & 6. The serving AMF will then pass on both the configured and thesubscribed S-NSSAI(s) to the NSSF together with the UE's assignedregistration area. NSSF examines both sets of S-NSSAI(s) and determineswhat are the allowed S-NSSAI(s) for the UE.

Based on the AMF to Core Network Slice Instance (NSI) mapping topologythat was provided by the operator's OAM system (e.g., the UE's servingPLMN), the NSSF then determines the set of mapping Core NSI(s) at theUE's registration area that are available to serve the UE. The set ofavailable Core NSI(s) are corresponding to the entire or the subset ofthe S-NSSAI(s) that were provided to the NSSF, and such finalcorresponding set of S-NSSAI(s) determined by the NSSF is referred asallowed NSSAI. In addition, the NSSF may determine a new serving AMFthat is better to serve the UE for the target set of available NSI(s).

7. NSSF responds to the current serving AMF with the set of availableCore NSI(s) that is mapped to the allowed NSSAI (e.g., the set ofallowed S-NSSAIs), the new serving AMF (e.g., identified by the IPaddress or fully qualified domain name FQDN), one or more serving NRFs(e.g., identified by the IP addresses or FQDNs) which serve thecorresponding available Core NSIs, and any additional slicing relatedpolicy (e.g. serving priorities among the available NSI(s) etc.).

8. The current serving AMF will cache all these info provided by theNSSF as part of the UE's context.

9. If a new serving AMF is indicated by the NSSF, the current servingAMF triggers the AMF relocation by coordinating with the 5G AccessNetwork (e.g. 5G RAN) to recognize the new AMF as the serving AMF. Thecurrent serving AMF will also pass on the UE's context to the newserving AMF.

10. The serving AMF will then inform the 5G Access Network for theallowed NSSAI (i.e. the set of S-NSSAIs that are mapped to the NSIswhich are available to serve the UE at the UE's registration area) andalso the identifier of the serving AMF (i.e. Temp ID) for the given UE.

11. The 5G Access Network also relay the final allowed NSSAI and theTemp ID to the UE, and the UE will store the info for later data sessionrequest for service activation.

IV.B. NSSF Notification to AMF on the NSI Topology or Policy Update

In some embodiments, a given AMF/AMF pool is dedicated to a specific setof Core NSIs to support the target S-NSSAIs. NSSF is aware of which AMFserves which set of Core NSI(s). If the Core NSI topology or policy ischanged by the operator's OAM system for the corresponding S-NSSAI,then, the AMF/AMF pool mapping to the Core NSI(s) will also be updatedin the NSSF with the changes. NSSF will propagate the update to theaffected AMF or AMF pool.

Two possible approaches for the NSSF to update the AMF or AMF pool forthe topology or policy changes:

NSSF pushes the topology update to the AMF or AMF pool, or

AMF or AMF pool pull the topology status periodically from the NSSFbased on periodic timer set topology check.

As a result of the AMF to Core NSI mapping topology change, either thegiven AMF/AMF pool continues to serve the same Core NSI or no longer toserve the same Core NSI.

IV.C. NSSF Operation During UE PDU Data Session Establishment

FIG. 7 describes the NSSF operation during the UE initiation for the PDUdata session establishment (i.e. network service activation) over the 5Gmobile network.

1. & 2. Application layer service activation triggers UE to performservice mapping to the allowed S-NSSAI.

3. UE initiates the data session request with the 5G system with therequested S-NSSAI, Temp-ID and the target data network (i.e. DNN).

4. & 5. 5G Access Network (e.g. 5G RAN) interprets the Temp-ID providedby the UE in order to route the UE's data session request to the targetserving AMF or AMF pool together with the requested S-NSSAI info andDNN. If 5G Access Network does not recognize the Temp-ID, the UE's datasession request will be routed to the default serving AMF or AMF pool.

6. By referring to the cached UE's context, if the current serving AMFor AMF pool detects that it is no longer serve the Core NSIcorresponding to the requested S-NSSAI (e.g. due to the Core NSItopology change), the serving AMF should verify with the NSSF with therequested S-NSSAI based on UE's current registration area to determinethe new target Core NSI and/or the new AMF to serve the UE.

Otherwise, skip this step-6 to 8 below and go to step-9.

7. The NSSF determines the new AMF to Core NSI mapping that iscorresponding to the requested S-NSSAI at the UE's registration area,and possible the revised allowed S-NSSAI to replace the old allowedS-NSSAI (i.e. replacing the requested S-NSSAI). In addition, the NSSFmay determine a new serving AMF that is better to serve the UE for themapping NSI.

The NSSF then respond to the serving AMF with the AMF to Core NSImapping (e.g., identified by the Core NSI ID) for the requested S-NSSAI,the possible new accepted S-NSSAI (i.e. replacement of the requestedS-NSSAI) and the new serving AMF (i.e. identified by the IP address orFQDN), the serving NRF (i.e. identified by the IP address or FQDN) andany additional slicing related policy (e.g. serving priorities among theavailable NSI(s) etc.).

8. If a new serving AMF is indicated by the NSSF, the old serving AMFtriggers the AMF relocation by coordinating with the 5G Access Network(e.g. 5G RAN) to recognize the new AMF as the serving AMF.

9. The serving AMF updates the UE's context and queries the serving NRFto discover and to select the proper SMF that serves the for theupcoming data session.

10. The serving AMF triggers the PDU data session establishmentprocedure with the newly selected SMF as requested by the UE. Upon thesuccessful data session establishment, the latest Temp-ID and the latestaccepted S-NSSAI will also be responded to the UE.

IV.D. Network Slicing Roaming Support Via NSSF

IV.D.1. During the UE's Registration (Home Routed Case)

FIG. 8 describes the UE registration during the network slicing roamingscenario, more specifically for the home routed case.

Steps 1., 2. & 3.: UE presents the “configured” NSSAI (referred asvPLMN(NSSAI)) that was provisioned for the target serving vPLMN to theRAN which refers to the NSSAI to route the registration request toselected serving vAMF.

4.: vAMF receives the UE's registration request and triggers the UE'sauthentication with the home UDM (hUDM).

5. vPLMN and hPLMN proceed with the UE's authentication.

6. & 7: Upon successful UE's authentication, serving AMF obtains theUE's subscribed NSSAI from hUDM (referred as hPLMN(NSSAI)).

8. & 9.: vAMF compiles the configured and subscribed NSSAI info fromboth UE and its home network and present them (e.g., vPLMN(NSSAI) andhPLMN(NSSAI)) as well as the UE's registration area to the vNSRF todetermine the “allowed” NSSAI to be used at the serving vPLMN.

10. & 11.: vNSSF communicates with the hNSSF to determine theavailability of the “allowed” NSSAI for the serving UE in the hPLMN andthe corresponding home core part of the NSIs (i.e. identified by thehome Core NSI IDs). hNSSF also provides the vNSSF for the address of thecorresponding home NRF (i.e. denoted as hPLMN(NRFs)) that serves thetarget NSI(s) to support the hPLMN network function selection anddiscovery.

12.: Based on the UE's registration area and the “allowed” NSSAI(including the related the CoreNSI ID), vNSSF determines the vNRF andthe possible new target vAMF as well as other necessary slice-levelcontrol policy.

13.: If new vAMF was indicated by the vNSSF, old serving vAMF triggersAMF redirection. Otherwise, skip this step and go to step 14.

14., 15. & 16.: Serving AMF caches all the slicing related context(received from 12 above) for the UE and responds to the UE for the“allowed” NSSAI as well as the Temp ID.

IV.D.2. During the PDU Session Establishment (Home Routed Case)

1: UE presents the “requested” NSSAI as well as the Temp ID to the RANwhich is eventually routed to the serving vAMF in the vPLMN.

2: (Assuming that the UE is still in the same registration area) vAMFrefers to the vNRF with the S-NSSAI to select the vSMF. As for theselection of the hSMF, there are two possible options.

Option-1: vAMF looks up from the hNRF with the S-NSSAI to identify thehSMF and then, vAMF pass the hSMF info to the vSMF (shown in FIG. 9).

Option-2: Once the vAMF selects the vSMF, vAMF passed on the hNRF andS-NSSAI info to the vSMF, then, the vSMF does the look up from the hNRFto select the hSMF (procedure depicted in FIG. 10).

IV.D.3. Roaming Hierarchy NRF Look-Up Optimization

Due to the privacy consideration, slice-level NRF look-up should belimited to the network function (NF) which is belonged to the same NSI.In the case of the roaming scenario, there will be multiple networkfunctions from the vPLMN (i.e. vNFs) to refer to the hNRF to look up forthe home network function belonged to the same NSI that it needs tocommunicate with.

In order to reduce the amount of peer-to-peer roaming interfaceinterconnections, this document introduces a designed entry point NRF(i.e. veNRF or heNRF) in both the visited and home PLMNs. The prefix “v”and “h” are used to indicate network functions and entities in a userdevice's visited network and home network. The veNRF and heNRF are aboveslice-level NRF based on the hierarchy structure of the NRF, to relaythe NRF look up. When the NF from the vPLMN performs their NRF look up,the slice-level NRF will relay the request towards the veNRF, which willthen communicate with the heNRF to relay such look up to the slice-levelhNRF. FIG. 11 describes the hierarchy NRF look up concept.

In some embodiments, a wireless communication system in which the NSSFis implemented as a separate entity in the network may be implemented.The NSSF may communicate with other network entities via an interfacecalled Nnssf.

In some embodiments, a network function repository function (NRF) thatincludes the NSSF may be implemented. The NRF provides the NSSF functionand further provides an isolation between network slices.

In some embodiments, a procedure for registering a user equipment (UE)in a mobile network may be implemented by a network-side server. Theprocedure includes receiving a network topology, and based on thenetwork topology, determining a set of network slice instances availablein the UE's registration area, and deciding whether to assign servingthe UE to a new serving AMF, and causing a current serving AMF to cacheinformation from the NSSF for future use.

In some embodiments, a network function that assigns a mobility functionfor serving network slice instances may be implemented. The networkfunction stores a mapping between a pool of the mobility functions and aset of core network slice instances being served by the pool, andselectively updating the mapping based on UE mobility or a change in anoperator policy or a topology of the mobile network.

In some embodiments, a method for establishing a packet data unit (PDU)session for may be implemented. During the establishing, a mobilityfunction uses locally cached information about a UE's context anddetermines its ability to serve the UE. If the mobility function is notable to serve the UE, the task of serving the UE is handed over to asecond mobility function.

In some embodiments, a network architecture that supports networkslicing roaming in a mobile network that uses home routing may beimplemented.

In some embodiments, a PLMN includes an entry point NRF that is adesignated entry point for communication with another PLMN's entry pointNRF and exchanges messages to manage a single connection point forcarrying NRF look-ups between the PLMNs.

In some embodiments, the NSSF function may be implemented by anapparatus that includes a memory, a processor and at least one networkinterface, wherein the processor reads instructions from the memory andimplements the NSSF function.

In some embodiments, the disclosed NSSF may be embodied as processorexecutable code and stored on a computer-readable program medium.

Some embodiments may be described based on the following examples.

Example 1

A method implemented by an apparatus operating in a public land mobilenetwork (PLMN), includes acquiring knowledge of access and mobilitymanagement (AMF) in the PLMN, implementing slice-level service mappingfor a given slice-specific Network Slice Selection Assistant Info(S-NSSAI), selecting a target network slice instance (NSI) based on oneor more operational parameters, identifying slice level policy fornetwork slices, and collecting slice-level statistics from AMF of itsserving PLMN and supports an NSSF's operation.

Example 2

The method of Example 1, wherein the one or more operational parametersinclude an identity of a serving network operator, an identity of aservice provider that is providing a requested service, location of auser equipment that is requesting a given network slice instance, a timeof day, or a network resource availability.

Example 3

The method of Example 1, wherein the apparatus of Example 1 isimplemented as a separate entity in the mobile network, and theapparatus communicating with other entities in the network via aper-defined communication interface.

Example 4

The method Example 1, further including implementing a network functionrepository by the apparatus of Example 1.

Example 5

The method of Example 4, further including implementing a logicalisolation between network slices.

Example 6

A method of registering a user equipment in a mobile network includesreceiving, at a network server, information about network topology ofthe mobile network, determining, based on the network topology, a set ofnetwork slice instances available in a user equipment's (UE)registration area, deciding to selectively assign serving the UE to anew serving mobility function, and causing a current serving mobilityfunction to cache information about the UE's context for future use.

Example 7

A method of assigning a mobility function for serving network sliceinstances, comprising storing a mapping between a pool of the mobilityfunctions and a set of core network slice instances being served by thepool, and selectively updating the mapping based on UE mobility or achange in an operator policy or a topology of the mobile network.

Example 8

A method for establishing a PDU session for a user equipment (UE)operating in a wireless communication network includes determining, by afirst mobility server from a pool of network-side servers, during theestablishing, using locally cached information about the UE's contextability of the network-side server to serve the UE, and selectivelyhanding over serving the UE to a second mobility function server in thepool based on the determining, when the first mobility server is notable to serve the UE.

Example 9

A method of providing network slicing roaming in a mobile network thatuses home routing includes receiving, from a user equipment (UE), aregistration request comprising the UE's network slice instanceassistant information (NSSAI), authenticating the UE for operation inthe mobile network, determining one or more allowed NSSAI from theconfigured NSSAI, and assigning a mobility function to serve the UEbased on the determining.

Example 10

The method of Example 9, wherein the determining the one or more allowedNSSAI includes exchanging messaging with a network slice servingfunction in the UE's home network.

Example 11

A method of providing network slicing roaming in a mobile network thatuses home routing includes receiving, from a user equipment (UE)operating in a visited network, a PDU session establishment requestcomprising the UE's requested network slice instance assistantinformation (NSSAI); looking up, from a mobility function in the visitednetwork, a set of NSSAI from the UE's network slice serving function inthe UE's home network; and passing information from the looking up to aserving mobility function in the visited network.

Example 12

A method of operating a public land mobile network (PLMN), comprisingdesignating an entry point network function repository function (NRF)for communication with another PLMN's entry point NRF, and exchangingmessages to manage a single connection point for carrying NRF look-upsbetween the PLMN and the another PLMN.

FIG. 12 shows an example hardware platform 1200 that may be used toimplement the various architectural blocks described herein. Forexample, the blocks shown in FIG. 4, FIG. 5, the NSSF, a user device, amobile device, a mobility function, a repository function, etc. may beimplemented using the hardware platform 1200. The hardware platform 1200may include a processor 1210. The hardware platform 1200 may implement acommunication interface 1220 such as the various interfaces shown inFIG. 1 to FIG. 5. The communication interface 1220 may be wired orwireless interface as appropriate. For example, some network functionsin the core network may comprise wired communication interface 1220,while user devices or mobile stations may comprise wirelesscommunication interfaces 1220. The processor 1210 may be configured toimplement the various techniques described in the present document. Inaddition, the hardware platform 1200 may be communicatively coupled withother hardware such as storage, database, memory, and so on.

FIG. 13 is a flowchart for an example method 1300 of facilitatingregistration of a mobile device in a communication network. Thecommunication network may be, for example, as depicted in FIG. 6. Themethod 1300 includes receiving (1302), at a network slice selectionfunction (e.g., NSSF) in a communication network, a network sliceinstance request message indicative of a configured network sliceselection assistance information for a user device is presentlyconfigured, a subscribed network slice selection assistance informationfor which the user device has subscribed, and an identity of aregistration area that the user device is associated with, andtransmitting (1304), in response to the network slice request message, aresponse message that includes information about allowed network sliceinstances for the user device. In some examples, a network slicecorresponds to a virtual logical network that is optimized for at leastone network service. In some examples, the allowed network sliceinstances comprise network slice instances from the registration areathat are available for the user device. For example, at 1302, themessage may be transmitted by a mobility function such as the AMF, andreceived by the network slice selection function. Section IV.A describessome additional features of method 1300.

In some embodiments, the method 1300 may include identifying, in theresponse message, a new serving mobility function for the user device(see, e.g., Step 7 of Section IV.A). In addition, as described inSection IV.A, in some embodiments, the response message may furtherinclude a priority rule related to the allowed network slice instances.For example, a priority rule may specify which ones of available networkslice instances has a higher priority for allocation or quality ofservice.

In some embodiments, the method 1300 may further include storing at thenetwork slice selection function, a mapping between access and mobilityfunctions and network slice instances available in the communicationnetwork. The storing may be performed such that the network sliceselection stores a system-wide mapping of mobility functions (e.g., AMF)and core part network slice instances for a given communication networksuch as a PLMN. For example, the mapping includes information about aset of active network slice instances corresponding to registrationareas in the communication network, and corresponding access andmobility function that is available for the set of active network sliceinstances. In addition, in some implementations, network slice instancelevel policies indicating priority among network slice instances asspecified in the communication network (e.g., PLMN) may also be stored.The method 1300 may perform a slice level mapping for a given networkslice selection assistance information, using operational parameterssuch as at least one of the user device's location, a time window, anidentify of a service provider for the communication network, and theuser device's current serving mobile network operator. As depicted inFIG. 4 and FIG. 5, the network slice selection function may beimplemented as a separate network function (e.g., using a separatehardware platform or platforms) that interacts with other networkfunctions using a standardized application programmers interface (API).In some implementations, e.g., as described in Section III.B, thenetwork slice selection function may be implemented by logicallypartitioning a network repository function into a first level operatingabove slice-level and configured to perform network level discovery andselection and a second level operating at slice-level and configured toperform slice level discover and selection.

FIG. 14 is a flowchart for an example method 1400 for facilitatingestablishment of a packet data session for a user device. For example,one implementation of the method 1400 is described in Section IV.C. Themethod 1400 includes, receiving (1402) a verification request from amobility function in a core network of a communication network, theverification request identifying the user device, a current registrationarea of the user device and a network slice assistance informationrequested by the user device for establishing the packet data session,and transmitting (1404) a response to the mobility function identifyinga network slice instance available for the network slice assistanceinformation requested by the user device. For example, the mobilityfunction may be the AMF. The method 1400 may further include identifyinganother mobility function that is suitable for serving the user device.The method 1400 may further include identifying, in the response, aslicing policy associated with the network slice instance. The responsemay further identify a revised allowed network slice assistanceinformation based on the another mobility function, such that therevised network slice assistance information replaces a previous allowednetwork slice information for the user device.

FIG. 15 is a flowchart for an example method 1500 of wirelesscommunication session performed during packet data session establishmentfor a user device. The method 1500 includes receiving (1502) by anetwork device in a wireless network a request for a data session from auser device, the data session request identifying an identification forthe user device and a target data network for the data session, andfacilitating (1504), further message exchanges in the wireless networkfor providing the packet data session to the user device. For example,this may include, selectively based on the identification for the userdevice, one of a default serving mobility function and a current servingmobility function for serving the request for the data session. Theidentification may be a temporary identification such that differentidentifications may be used for different packet date establishmentsessions.

FIG. 16 is a flowchart for an example method 1600 of operating an entrypoint function in a communication network. Section IV.D.3 describes oneexample embodiment of method 1600. The method 1600 may be implemented ina communication network comprising a first PLMN and a second PLMN. Themethod 1600 includes operating (1602) an entry point function in thefirst PLMN at a logical level above a first plurality of slice levelrepository functions in the first PLMN to receive resource look-uprequests from a second plurality of slice level repository functions inthe second PLMN, and communicating (1604) with the first plurality ofslice level repository functions in the first PLMN to generate aresponse for the resource look-up requests. In various embodiments, thefirst and the second PLMNs may be home or visited PLMNs and vice versa.

FIG. 17 is a flowchart for an example method 1700 of wirelesscommunication implemented by a mobile device. Some example embodimentsare described in Section IV.A. The method 1700 includes registering(1702) for operation in the wireless network using network sliceassistance information for which the mobile device is configured, andindicating a target set of network services that the mobile devicewants, receiving (1704) a set of allowed network slice assistanceinformation and a session identification, and performing (1706) furthercommunication in the wireless network using the set of allowed networkslice assistance information and the session identification. The mobiledevice may further map services requested by application level triggersto the allowed network slice instance assistance information, andtrigger a data session request in response to the application leveltriggers by using the mapping.

FIG. 18 is a flowchart for an example method 1800 for providing networkservices to a mobile device operating in a vested network. The method1800 includes receiving (1802), by a mobility function in the visitednetwork, from the mobile device, a message identifying requested networkslice assistance information and an identification of the mobile device,obtaining (1804) identification of a session management function in ahome network for the mobile device, wherein the obtaining is performedquerying a network repository function in the home network for themobile device with the requested network slice assistance information,and providing (1806) the identification of the session managementfunction in the home network to a session management function in thevisited network. In some embodiments, the mobility function in thevisited network may cache a network slice information context of themobile device during a registration of the mobile device in the visitednetwork.

FIG. 19 is a flowchart for another example method 1900 for providingnetwork services to a mobile device operating in a visited network. Themethod 1900 may be implemented by a mobility function such as the AMF.The method 1900 includes receiving (1902), by a mobility function in thevisited network, from the mobile device, a message identifying requestednetwork slice assistance information and an identification of the mobiledevice, selecting (1904) a session management function serving thevisited network, and providing (1906) identification of a networkrepository function in a home network for the mobile device and therequested network slice assistance information to the session managementfunction serving the visited network for the session management functionserving the visited network to look up a session management function inthe home network for the mobile device.

In some embodiments, the mobility function may cache a network sliceinformation context of the mobile device during a registration of themobile device in the visited network.

It will be appreciated that the present document discloses a new networkfunction called network slice selection function NSSF that can beimplemented in the core network of a communication network (e.g., 5Gcommunication network). The NSSF tracks available NSI in a givenregistration area and coordinates allocation of proper network resourcesto meet service demands from a user device. The NSSF may achieve thecoordination by interacting with the AMF and with NSSF function in themobile device's visited network.

The disclosed and other embodiments, modules and the functionaloperations described in this document can be implemented in digitalelectronic circuitry, or in computer software, firmware, or hardware,including the structures disclosed in this document and their structuralequivalents, or in combinations of one or more of them. The disclosedand other embodiments can be implemented as one or more computer programproducts, i.e., one or more modules of computer program instructionsencoded on a computer readable medium for execution by, or to controlthe operation of, data processing apparatus. The computer readablemedium can be a machine-readable storage device, a machine-readablestorage substrate, a memory device, a composition of matter effecting amachine-readable propagated signal, or a combination of one or morethem. The term “data processing apparatus” encompasses all apparatus,devices, and machines for processing data, including by way of example aprogrammable processor, a computer, or multiple processors or computers.The apparatus can include, in addition to hardware, code that creates anexecution environment for the computer program in question, e.g., codethat constitutes processor firmware, a protocol stack, a databasemanagement system, an operating system, or a combination of one or moreof them. A propagated signal is an artificially generated signal, e.g.,a machine-generated electrical, optical, or electromagnetic signal, thatis generated to encode information for transmission to suitable receiverapparatus.

A computer program (also known as a program, software, softwareapplication, script, or code) can be written in any form of programminglanguage, including compiled or interpreted languages, and it can bedeployed in any form, including as a stand alone program or as a module,component, subroutine, or other unit suitable for use in a computingenvironment. A computer program does not necessarily correspond to afile in a file system. A program can be stored in a portion of a filethat holds other programs or data (e.g., one or more scripts stored in amarkup language document), in a single file dedicated to the program inquestion, or in multiple coordinated files (e.g., files that store oneor more modules, sub programs, or portions of code). A computer programcan be deployed to be executed on one computer or on multiple computersthat are located at one site or distributed across multiple sites andinterconnected by a communication network.

The processes and logic flows described in this document can beperformed by one or more programmable processors executing one or morecomputer programs to perform functions by operating on input data andgenerating output. The processes and logic flows can also be performedby, and apparatus can also be implemented as, special purpose logiccircuitry, e.g., an FPGA (field programmable gate array) or an ASIC(application specific integrated circuit).

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. Generally, aprocessor will receive instructions and data from a read only memory ora random access memory or both. The essential elements of a computer area processor for performing instructions and one or more memory devicesfor storing instructions and data. Generally, a computer will alsoinclude, or be operatively coupled to receive data from or transfer datato, or both, one or more mass storage devices for storing data, e.g.,magnetic, magneto optical disks, or optical disks. However, a computerneed not have such devices. Computer readable media suitable for storingcomputer program instructions and data include all forms of non-volatilememory, media and memory devices, including by way of examplesemiconductor memory devices, e.g., EPROM, EEPROM, and flash memorydevices; magnetic disks, e.g., internal hard disks or removable disks;magneto optical disks; and CD ROM and DVD-ROM disks. The processor andthe memory can be supplemented by, or incorporated in, special purposelogic circuitry.

While this document contains many specifics, these should not beconstrued as limitations on the scope of an invention that is claimed orof what may be claimed, but rather as descriptions of features specificto particular embodiments. Certain features that are described in thisdocument in the context of separate embodiments can also be implementedin combination in a single embodiment. Conversely, various features thatare described in the context of a single embodiment can also beimplemented in multiple embodiments separately or in any suitablesub-combination. Moreover, although features may be described above asacting in certain combinations and even initially claimed as such, oneor more features from a claimed combination can in some cases be excisedfrom the combination, and the claimed combination may be directed to asub-combination or a variation of a sub-combination. Similarly, whileoperations are depicted in the drawings in a particular order, thisshould not be understood as requiring that such operations be performedin the particular order shown or in sequential order, or that allillustrated operations be performed, to achieve desirable results.

Only a few examples and implementations are disclosed. Variations,modifications, and enhancements to the described examples andimplementations and other implementations can be made based on what isdisclosed.

What is claimed is:
 1. A method of facilitating network slicingoperation in a wireless communication network, comprising: receiving, ata network slice selection function in a communication network, from anaccess and mobility function in the communication network to which aregistration request from a user device is routed, a network sliceinstance request of a configured slice specific network slice selectionassistance information that is presently configured for the user device,a subscribed slice specific network slice selection assistanceinformation for which the user device has subscribed, and an identity ofa registration area that the user device is associated with;determining, by the network slice selection function, a set of corenetwork slice instances that is available at the registration area toserve the user device and a final corresponding set of slice specificnetwork slice selection assistance information; and transmitting, by thenetwork slice selection function and in response to the network sliceinstance request, the final corresponding set of slice specific networkslice selection assistance information.
 2. The method of claim 1,further including: identifying a new serving mobility function for theuser device.
 3. The method of claim 1, further including: identifying aset of repository functions that provide network function registrationand discovery for the set of core network slice instances for the userdevice.
 4. The method of claim 1, further including, storing, at thenetwork slice selection function, a mapping between access and mobilityfunctions and network slice instances available in the communicationnetwork.
 5. The method of claim 1, wherein the network slice selectionfunction is implemented as a logically separate network function in thecommunication network, and wherein the network slice selection functioncommunicates with other entities in the communication network using apre-defined interface.
 6. The method of claim 1, wherein the networkslice selection function is implemented by logically partitioning anetwork repository function into a first level operating aboveslice-level and configured to perform network level discovery andselection and a second level operating at slice-level and configured toperform slice level discover and selection.
 7. A communication apparatuscomprising a processor configured to implement a method comprisingfollowing steps: receiving, at a network slice selection function in acommunication network, from a serving access and mobility function inthe communication network to which a registration request from a userdevice is routed, a network slice instance request of a configured slicespecific network slice selection assistance information that ispresently configured for the user device, a subscribed slice specificnetwork slice selection assistance information for which the user devicehas subscribed, and an identity of a registration area that the userdevice is associated with; determining, by the network slice selectionfunction, a set of core network slice instances that is available at theregistration area to serve the user device and a final corresponding setof slice specific network slice selection assistance information; andtransmitting, by the network slice selection function and in response tothe network slice instance request, the final corresponding set of slicespecific network slice selection assistance information.
 8. Thecommunication apparatus of claim 7, wherein the processor is furtherconfigured for: identifying a new serving mobility function for the userdevice.
 9. The communication apparatus of claim 7, wherein the processoris further configured for: identifying a set of repository functionsthat provide network function registration and discovery for the set ofcore network slice instances for the user device.
 10. The communicationapparatus of claim 7, wherein the network slice selection function isimplemented as a logically separate network function in thecommunication network, and wherein the network slice selection functioncommunicates with other entities in the communication network using apre-defined interface.
 11. The communication apparatus of claim 7,wherein the network slice selection function is implemented by logicallypartitioning a network repository function into a first level operatingabove slice-level and configured to perform network level discovery andselection and a second level operating at slice-level and configured toperform slice level discover and selection.
 12. A computer programproduct comprising a computer readable memory having code storedthereupon, the code, when executed, causing a processor to implement amethod of facilitating network slicing operation in a wirelesscommunication network, comprising: receiving, at a network sliceselection function in a communication network, from an access andmobility function in the communication network to which a registrationrequest from a user device is routed, a network slice instance requestof a configured slice specific network slice selection assistanceinformation that is presently configured for the user device, asubscribed slice specific network slice selection assistance informationfor which the user device has subscribed, and an identity of aregistration area that the user device is associated with; determining,by the network slice selection function, a set of core network sliceinstances that is available at the registration area to serve the userdevice and a final corresponding set of slice specific network sliceselection assistance information; and transmitting, by the network sliceselection function and in response to the network slice instancerequest, the final corresponding set of slice specific network sliceselection assistance information.
 13. The computer program product ofclaim 12, wherein the method further includes: identifying a new servingmobility function for the user device.
 14. The computer program productof claim 12, further including: identifying a set of repositoryfunctions that provide network function registration and discovery forthe set of core network slice instances for the user device.
 15. Thecomputer program product of claim 12, wherein the method furtherincludes implementing the network slice selection function as alogically separate network function in the communication network, andwherein the network slice selection function communicates with otherentities in the communication network using a pre-defined interface.